Apparatus and method for feeding material from storage bins and the like

ABSTRACT

Aggregate material, such as wood chips, is metered from the bottom of a storage bin by means of two bands of screw conveyors which are operated alternately in order to overcome the effects of bridging of the aggregate stored in the bin.

United States Patent [191 Gatz et a1.

[451 Jan. 15,1974

1 1 APPARATUS AND METHOD FOR FEEDING MATERIAL FROM STORAGE BINS AND THE LIKE [75] Inventors: William L. Gatz; Kenneth A.

Rennicke, both of Paragould, Ark.

[73] Assignee: Royal Industries, Pasadena, Calif.

22 Filed: June 19', 1972 [21] Appl. No.: 264,253

[521' US. Cl. 214/17 D, 222/52 [51] Int. Cl. B65g 65/30 [58] Field of Search 1.98/64, 32, 78-80;

[56] References Cited UNITED STATES PATENTS 3,122,231 2/1964 Pence 198/78 2,978,092 4/1961 Phillips 198/32 Primary ExaminerEdward A. Sroka Att0meyShapiro & Shapiro 5 7 ABSTRACT Aggregate material, such as wood chips, is metered from the bottom of a storage bin by means of two bands of screw conveyors which are operated alternately in order to overcome the effects of bridging of the aggregate stored'in the bin.

17 Claims, 5 Drawing Figures PAiENIED- wasmz saw 2 a; 3

BACKGROUND OF THE INVENTION This invention relates to apparatus and methods for feeding material from a storage bin or the like and is more particularly concerned with a system for metering stored aggregate material in a manner which overcomes the bridging nature of the material.

It is common practice to store large quantities of aggregate material in storage bins or other accumulators, from which the material may be rapidly dumped into a truck, for example. Many types of aggregate material tend to link or agglomerate when stored in bulk. For example, wood chips stored in a bin tend to interlock to form an interdependent network in a relatively stable pile that resist flowing. The natural tendency of such material to become entangled in itself produces bridging of the material above the outlet of a bulk storage container, and the flow of material from beneath a bridge produces a cavity in the bulk pile.

It has been known that by properly selecting the slope angle of the bin sidewalls and by providing an adequate opening at the bottom of the bin to permit'rapid discharge, the gross weight of the total load of material within the bin tends to overcome the bridging nature of the material, and the material falls freely from the bin as a mass when the retaining doors or gates at the bottom of the bin are open. Such bins are shown, for example, in U.S. Pat. No. 3,319,807 issued to Van Raden on May 16, 1967.

When an attempt is made to feed aggregate material from the bottom of a bin, such as the aforesaid Van Raden bin, at a relatively slow, even rate, any bridging tendency of the material impedes and interrupts the flow. Metering of the material from the bin, as by the use of screw conveyors, becomes impossible on a continuous basis. It hasbeen proposed to place agitators in the bin in order to prevent the formation of bridges and to assist feeding. See, for example, US. Pat. No. 3,602,380 issued to Spencer on Aug. 31, 197 l. The addition of agitators requires bin modification and has other disadvantages.

BRIEF DESCRIPTION OF THE INVENTION It is accordingly a principal object of the present invention to provide an improvedapparatus and method for feeding material from a bin or other accumulator in a manner which overcomes the natural bridging tendency of thematerial and which permits the material to be metered from the accumulator slowly and continuously.

Another object of the invention is to provide appartus and methods of the foregoing type which overcome the effects of bridging by feeding material in a manner which unbalances the static forces required to maintain bridging.

A further object of the invention is to provide an improved apparatus and method for supplying aggregate material at steady flow ratesfor fuel supply, for batch mixing or blending, or for any other appropriate application.

Still another object of the invention is to provide an improved live bottom feeder which may readily be added to a conventional bin;

Briefly stated, in accordance with a preferred embodiment of the present invention, two banks of screw conveyors are employed to feed material from the bottom of a bulk storage container. The banks are driven independently but are controlled interdependently. Under normal running conditions following start-up, only one bank will operate at a time. If bridging occurs over the operating bank, the other bank will be rendered operative instead, thereby continuing the flow of material and at the same time creating unbalance in the forces required to sustain the bridge.

BRIEF DESCRIPTION OF THE DRAWINGS The inventiion will be further described in conjunction with the accompanying drawings, which illustrate .a preferred and exemplary embodiment, and wherein:

FIG. 1 is a partly diagrammatic top plan view of feeder apparatus in accordance with the invention, illustrating two banks of screw conveyors supplying a single collection screw conveyor, and also a motor control circuit for controlling the operation of the conveyor banks in response to load-sensors; FIG. 2 is a side elevation view of the feeder apparatus of FIG. 1, showing the bottom portion of a bin above the feeder apparatus and showing an auxiliary conveyor;

FIG. 3 is an end elevation view illustrating feeder apparatus of the invention installed under an existing storage bin;

FIG. 4 is an end elevation view of the feeder apparatus, with the casing partially broken away; and

FIG. 5 is a diagram of the motor control circuit.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, and initially to FIGS. 1 and 2 thereof, feeder apparatus 10 of the invention comprises a pair of conveyors 12 and 14, preferably two banks of screw conveyors 15 supported upon a framework 16 in separate compartments divided by a wall 18. The screw conveyors, which may be any appropriate conventional type, are driven independently by electric motors 20 and 22 through the usual drive trains. Both conveyors feed material in the direction of arrows 24. A collection conveyor 26 may be employed to transfer the material fed by conveyors l2 and 14 to a common discharge point or outlet. In the form shown, the collection conveyor comprises a single screw with a pair of opposite pitch sections driven by an electric 7 motor 28 so as to convey the material to a central discharge point, as indicated by the arrows 30. As shown in FIGS. 2 and 4, the collection conveyor 26 may be located in a trough below one end of the conveyors 12 and 14, and the central discharge point of the collection conveyor maybe connected to the inlet 32 of an auxiliary conveyor, such as a pneumatic conveyor 34. As will be described more fully hereinafter, motors 20, 22, and 28 are controlled by a motor control circuit 36, shown generally in FIG. 1, in response to load sensors 38 and 40 which detect the presence or absence of material above the inlets of conveyors l2 and 14.

As shown in FIGS. 2 and 3, the feeder apparatus of the invention may be employed to feed material from an accumulator, such as a storage bin 42. The storage bin, which may be of the type disclosed in the aforesaid Van Raden patent, for example, may have suitable means 44 at the top (FIG. 3) for filling the bin with material and may have gates or doors 46 at the bottom,

which are opened to release material from the bin 42 through a discharge opening. The feeder apparatus of the invention may be supported on the bin frame beneath the discharge opening so that the bin contents are supplied to fill a low hopper 47 above the conveyors l2 and 14. Before turning to the electrical system and the manner in which the invention operates as a live bottom feeder to meter the material from bin 42, it will be noted in FIGS. 2 and 4 that doors 48 hinged at 50 may be provided above the collection conveyor 26. If either section of the collection conveyor becomes overloaded, the corresponding door will rise and actuate a switch 52, to de-energize motors and 22 as will appear more fully hereinafter.

The electrical system of the invention, including the motor control circuit 36 of FIG. 1, the load sensors 38 and 40, door switches 52, and a pneumatically actuated cut-off switch 54 is shown in FIG. 5. Motors 20 and 22 for driving conveyors 12 and 14 (which by reference to FIG. 1 will be referred to as the left bank and right bank of screw conveyors, respectively) and motor 28 for driving the collection screw conveyor 26 are energized from power lines L L and L by motor starter units 56, 58 and 60, respectively. The motor starter units include the usual solenoids 62, 64 and 66 for closing main contacts 68, 70 and 72 in order to energize the respective motors. Solenoids 62 and 64 actuate normally closed contacts 74 and 76, respectively, as well as the main motor contacts. The motor starter units may also have conventional reset contacts 78, 80, and 82.

Motor-starter solenoid 66 for motor 28 has one side connected to line L through the reset contacts 82 and the other side connected to line L through a section of switch 54. Motor-starter solenoids 62 and 64 for motors 20 and 22, respectively, have one side connected to line L through switches 52, another section of switch 54, and the appropriate reset contacts 78 or 80. The other side of each of solenoids 62 and 64 is connected to an associated junction point 82 or 84, from each of which a path to power line L, may be completed by either of two circuits. Thus, one curcuit may be traced from junction point 82 through conductor 86, contact 87 of a single-pole double-throw switch 40R and conductor 88 to line L,. A further circuit may be traced from junction point 82 through conductor 90, contacts 76 of motor controller unit 58, and contact 91 of switch 40R and conductor 88 to line L Similar circuits may be traced from junction point 84 through contact 93 of single-pole double-throw switch 38L to line L, and through contacts 74 of motor controller 56 and contact 95 of switch 38L to line L When either of door switches 52 is opened, the energization circuit for solenoids 62 and 64 is broken, deenergizing motors 20 and 22. As indicated above, switches 52 open in the event of an overload in either section of the collector screw conveyor 26. When switches 54 open, all three conveyor motors 20, 22 and 28, are de-energized. Switches 54 may be conventional pneumatically actuated switches which sense the pressure in pneumatic conveyor 34 and prevent the operation of the motors 20, 22 and 28 until the pneumatic pressure (vacuum) reaches a predetermined level.

Switches 38L and 40R are part of the corresponding load sensors 38 and 40 indicated in FIGS. 1 and 2. Such load sensors are conventionally employed in storage bins to control and indicate bin supply levels and may, for exampleybe of the type manufactured by the Monitor or Bindicator Company, which incorporate motordriven paddles within the bin and which operate switches, such as switches 38L and 40R, in response to the presence or absence of a sufficient load (the bin contents) upon the paddles. A suitable sensor is the Type 2, Model R Roto Bin-Dicator, manufactured by Bindicator Company, 915 Dove Street, Port Huron, Michigan. The load sensors 38 and 40 (FIGS. 1 and 2) may be positioned near the bin discharge opening, with one sensor being positioned above each of the conveyor banks 12 and 14, so as to determine whether the material at the bin discharge opening is sufficient to supply each of the conveyor banks.

Three basic operating conditions may exist in accordance with the invention. Condition 1 exists prior to the filling of the bins, both sensors 38 and 40 indicating no load, and switches 38L and 40R being closed upon contacts 93 and 87 as illustrated in FIG. 5. Both of motor-starter solenoids 62 and 64 will be energized, because energization circuits will be completed from junction points 82 and 84 through contacts 87 and 93 of switches 40R and 38L, respectively. Motors 20 and 22 will both be operative (as well as motor 28). Energization of motor-starter solenoids 62 and 64 will open contacts 74 and 76, but the opening of these contacts at this time will have no effect.

Condition 2 will exist, for example, when the bin starts to fill (as from the top feeder 44 of FIG. 2) and sufficient material is present over one of the load sensors to cause this sensor to transfer its switch contacts. For example, it may be assumed that sensor 38 is loaded and that switch 38L closes upon contact 95, opening the circuit through contact 93. Because of the manner in which the bin is usually filled from the top (one side filled first), one sensor will normally indicate a load before the other. When the loaded sensor transfers its contacts, the energization circuit for the motorstarter solenoid of the conveyor motor associated with the opposite side of the bin will be broken, deenergizing that motor. Thus, with switch 38L closed upon contact 95, the energization circuit to junction point 84 of solenoid 64 through contact 93 will be interrupted. The circuit to this junction point through contacts 74 of motor controller unit 56 is already interrupted due to energization of solenoid 62. Thus, motor 22 and the associated conveyor bank will cease operation.

Under condition 3, both load sensors 38 and 40 will indicate load. This condition will occur, for example, as material continues to be added to the bin, causing sensor switch 40R to close upon contact 91. Although this transfer of contacts breaks the energization circuit to junction point 82 of solenoid 62 through contact 87 of switch 40R, it completes a circuit to junction point 82 through contact 91 of switch 40R and through contacts 76, which are now closed due to the previous deenergization of solenoid 70. Solenoid 62 remains energized (switch 40R transfers fast enough to prevent drop-out), and motor 20 remains energized.

Condition 3 will remain in effect until the sensor (assumed 38) on the same side of the bin as the operative conveyor indicates an impediment to the supply of material (no load), either because the material on this side has become exhausted or because of bridging at the outlet of the bin, as indicated by the link B in FIG. 2. When this occurs, sensor switch 38L will transfer again, completing a circuit through contact 93 to junction point 84 of solenoid 64 and energizing motor 22 associated with the conveyor at the other side of the bin. The energization of solenoid 64 will open contacts 76, breaking the circuit to junction point 82 from contact 91 of switch 40R and de-energizing solenoid 62 and motor 20. When sensor 38 becomes loaded again, switch 38L will close upon contact 95, breaking the circuit to junction point 84 through contact 93, but also completing a circuit through contact 95 and closed contacts 74. Motor will remain de-energized and motor 22 energized until a no-load condition is sensed by sensor 40, whereupon sensor switch 40R will transfer its contacts, completing an energization circuit through contact 87 to junction point 82 for solenoid 62. The energization of solenoid 62 (and motor 20) will open contacts 74 breaking the circuit to junction point 84 through contacts 74 and de-energizing solenoid 64 and motor 22.

The mode of operation just set forth presumes that when the sensor on the same side of the bin as the operative conveyor bank becomes unloaded due to a low level or bridging condition (energizing the motor on the opposite side and thereupon de-energizing thepreviously energized motor) the circumstances which caused the unloading of the sensor will thereafter be corrected. If the unloading of the sensor is due to low bin contents level, this will be corrected by the addition of material to the bin. It is common practice to employ bin level indicators (at a level above sensors 38 and 40) to control the automatic addition of material to the bin when the supply is low. lf the unloading of the sensor is due to bridging of the bin contents above the sensor, this will be corrected by, virtue of the unbalancing of the bridge-sustaining forces which takes place when the conveyor bank on the opposite side of the bin starts to operate and the material starts to flow.

Under normal running conditions, after the bin has begun to fill, only one of the conveyor banks will be operating. The other conveyor bank will'become operative in place of the operating bank when the operating bank has an insufficientsupply of material at its inlet. The conveyor banks cycle back and forth as required by the operating conditions referred to above. A man-' ual override switch may be employed to shunt switches 74 and 76 in order to energize both conveyor banks simultaneously when desired. Also, conveyor speed controllers may be employed to vary the flow rate. By virtue of the invention, it is possible to provide low volume and steady discharge rates without the usual interruptions due to bridging or cavitation. Moreover, the invention can readily be added to a conventional high volume discharge storage bin to provide a low volume discharge live bottom feeder.

While a preferred embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that changes can be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims.

The invention claimed is:

1. ln apparatus of the type described: a bulk storage container; first and second independently driven conveyor means for feeding material from said storage container toward an outlet; means for energizing said second conveyor means; and means for energizing said first conveyor means in response to impediment to the feeding of material to said outlet by said second conveyor means.

2. Apparatus in accordance with claim 1, wherein said means for energizing said first conveyor means is responsive to an impediment to the supply of material to said second conveyor means from said storage container.

3. In apparatus of the type described: first and second independently driven conveyor means for feeding material toward an outlet; means for energizing said first conveyor means in response to an impediment to the supply of material to said second conveyor means; and means responsive to the occurrence of said impediment, for de-energizing said second conveyor means.

4. Apparatus in accordance with claim 3, further comprising means responsive to the occurrence of an impediment to the feeding of material to said outlet by said first conveyor means for energizing said'second conveyor means and de-energizing said first conveyor means.

5. Apparatus in accordance with claim 4, wherein said conveyor means have a common storage container means for supplying material to both conveyor means.

6. Apparatus in accordance with claim 5, wherein said container means is a bin having a discharge opening at the bottom and said conveyor means are located one adjacent to the other beneath said discharge opening.

7. Apparatus in accordance with ,claim 6, wherein each of said conveyor means comprises a bank of screw conveyors.

8. Apparatus in accordance with claim 7, further comprising an additional conveyor means for conveying material from the aforesaid conveyor means to said outlet. I

9. Apparatus in accordance with claim 5, wherein said first and second conveyor means are driven by first and second electric motors, respectively, wherein said means for energizing said first and second conveyor means, respectively, comprises first and second sensor switch means for sensing the supply of material to said second and said first conveyor means, respectively.

10. Apparatus in accordance with claim 9, wherein each sensor switch means has means for providing alternate circuits for energizing the motor of the associated conveyer means, each sensor switch means selecting one of its alternate circuits in response'to the sensing of an insufficient supply by that sensor which means and selecting the other of its alternate circuits in response to the sensing of a sufficient supply by that sensor switch means, and a pair of further switch means, one connected in each of said other circuits, the further switch means connected in the other circuit of said .first sensor switch means being closed upon deenergization of the motor which drives the second conveyor means, and the further switch means connected to the other circuit of said second sensor switch means being closed upon de-energization of the motor which drives the first conveyor means.

11. Material feeder apparatus comprising a pair of conveyor means, a pair of motors for driving said conveyor means, respectively, means for supplying material to said conveyor means, and means for causing said motors to operate alternately and cyclically, the lastmentioned means including a pair of sensing means, one sensing means for sensing the supply of material at one conveyor means and for controlling the operation of the motor of the other conveyor means, and the other sensing means for sensing the supply of material at said other conveyor means and controlling the operation of the motor of said one conveyor means.

12. Apparatus in accordance with claim 11, wherein each of said motors has a pair of circuits for controlling the energization thereof, means responsive to the energization of one motor for controlling the flow of current through one of the energization circuits of the other motor, and means responsive to the energization of the other motor for controlling the flow of current through one of the energization circuits of said one mo- 01.

13. A method of feeding material from the bottom discharge opening of a bulk supply container, which comprises providing feed conveyors under two portions of said discharge opening, energizing one of said conveyors, sensing an impediment to the supply of material to said one conveyor, and thereupon energizing the other conveyor and de-energizing said one conveyor.

14. A method in accordance with claim 13, wherein the impediment sensed is due to bridging of said material, and the energization of the other conveyor relieves the bridging.

15. A method in accordance with claim 13, further comprising sensing an impediment to the supply of material to said other conveyor, and thereupon energizing said one conveyor and de-energizing said other conveyor.

16. A method in accordance with claim 15, wherein the energization of said conveyors cycles between them.

17. A method in accordance with claim 13, wherein both conveyors are initially energized, when the supply of material to both is impeded, and then one of them is de-energized when the supply of material to the other is no longer impeded. 

1. In apparatus of the type described: a bulk storage container; first and second independently driven conveyor means for feeding material from said storage container toward an outlet; means for energizing said second conveyor means; and means for energizing said first conveyor means in response to impediment to the feeding of material to said outlet by said second conveyor means.
 2. Apparatus in accordance with claim 1, wherein said means for energizing said first conveyor means is responsive to an impediment to the supply of material to said second conveyor means from said storage container.
 3. In apparatus of the type described: first and second independently driven conveyor means for feeding material toward an outlet; means for energizing said first conveyor means in response to an impediment to the supply of material to said second conveyor means; and means responsive to the occurrence of said impediment, for de-energizing said second conveyor means.
 4. Apparatus in accordance with claim 3, further comprising means responsive to the occurrence of an impediment to the feeding of material to said outlet by said first conveyor means for energizing said second conveyor means and de-energizing said first conveyor means.
 5. Apparatus in accordance with claim 4, wherein said conveyor means have a common storage container means for supplying material to both conveyor means.
 6. Apparatus in accordance with claim 5, wherein said container means is a bin having a discharge opening at the bottom and said conveyor means are located one adjacent to the other beneath said discharge opening.
 7. Apparatus in accordance with claim 6, wherein each of said conveyor means comprises a bank of screw conveyors.
 8. Apparatus in accordance with claim 7, further comprising an additional conveyor means for conveying material from the aforesaid conveyor means to said outlet.
 9. Apparatus in accordance with claim 5, wherein said first and second conveyor means are driven by first and second electric motors, respectively, wherein said means for energizing said first and second conveyor means, respectively, comprises first and second sensor switch means for sensing the supply of material to said second and said first conveyor means, respectively.
 10. Apparatus in accordance with claim 9, wherein each sensor switch means has means for providing alternate circuits for energizing the motor of the associated conveyer means, each sensor switch means selecting one of its alternate circuits in response to the sensing of an insufficient supply by that sensor which means and selecting the other of its alternate circuits in response to the sensing of a sufficient supply by that sensor switch means, and a pair of further switch means, one connected in each of said other circuits, the further switch means connected in the other circuit of said first sensor switch means being closed upon de-energization of the motor which drives the second conveyor means, and the further switch means connected to the other circuit of said second sensor switch means being closed upon de-energization of the motor which drives the first conveyor means.
 11. Material feeder apparatus comprising a pair of conveyor means, a pair of motors for driving said conveyor means, respectively, means for supplying material to said conveyor means, and means for causing said motors to operate alternately and cyclically, the last-mentioned means including a pair of sensing means, one sensing means for sensing the supply of material at one conveyor means and for controlling the operation of the motor of the other conveyor means, and the other sensing means for sensing the supply of material at said other conveyor means and controlling the operation of the motor of said one conveyor means.
 12. Apparatus in accordance with claim 11, wherein each of said motors has a pair of circuits for controlling the energization thereof, means responsive to the energization of one motor for controlling the flow of current through one of the energization circuits of the other motor, and means responsive to the energization of the other motor for controlling the flow of current through one of the energization circuits of said one motor.
 13. A method of feeding material from the bottom discharge opening of a bulk supply container, which comprises providing feed conveyors under two portions of said discharge opening, energizing one of said conveyors, sensing an impediment to the supply of material to said one conveyor, and thereupon energizing the other conveyor and de-energizing said one conveyor.
 14. A method in accordance with claim 13, wherein the impediment sensed is due to bridging of said material, and the energization of the other conveyor relieves the bridging.
 15. A method in accordance with claim 13, further comprising sensing an impediment to the supply of material to said other conveyor, and thereupon energizing said one conveyor and de-energizing said other conveyor.
 16. A method in accordance with claim 15, wherein the energization of said conveyors cycles between them.
 17. A method in accordance with claim 13, wherein both conveyors are initially energized, when the supply of material to both is impeded, and then one of them is de-energized when the supply of material to the other is no longer impeded. 